Field of the Invention
The present invention relates to a method for fabricating a field-effect-controllable semiconductor component having a first terminal zone and a second terminal zone of a first conduction type, a channel zone arranged between the first terminal zone and the second terminal zone, and a control electrode, which is formed in a manner insulated from the terminal and channel zones and runs in the vertical direction. The terminal zones are contact-connected by using electrodes. In a MOSFET (Metal Oxide Semiconductor Field Effect Transistor), the first terminal zone is usually referred to as the drain zone, the second terminal zone is usually referred to as the source zone, the channel zone is usually referred to the as body zone and the control electrode is usually referred to the as gate electrode. Such components with a component arranged in a trench are also referred to as trench transistors.
The invention relates, in particular, to the fabrication of the source zone in such a way that a low-resistance contact is formed between the terminal zone and the associated terminal electrode. The second terminal zone is usually fabricated by redoping the channel zone in the region of the front side of the semiconductor body. In order to fabricate a low-resistance contact between a later electrode and the second terminal zone, the second terminal zone is highly doped, that is to say, by way of example, high doses of dopants of the second conduction type are implanted. In trench transistors, the following problem can occur in this case:
A high dopant concentration also ensues in the semiconductor region directly adjacent to the insulation layer of the gate electrode. A section of the body zone along the insulation layer, which section remains after this doping, serves for forming a conductive channel between the source zone and the drain zone when a drive potential is applied. The length of this channel running in the vertical direction—and hence the parameters which are relevant to the switching behavior and the breakdown behavior, such as, for example, the breakdown voltage and the threshold voltage—are determined by the penetration depth of the dopant atoms in the vertical direction during the method for fabricating the source zone. In known methods, the entire front side of the semiconductor body is exposed to the implantation process. Since the gate electrode usually ends below the surface of the semiconductor body, or is etched back correspondingly, dopant atoms can be scattered via the cutout above the gate electrode through the insulation layer into the body zone and can shorten the available channel region.
A remedy may be provided by reducing the implantation dose or the implantation energy, although this increases the contact resistance between a later source electrode and the source zone.